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Quantitation of LMW-GS to HMW-GS Ratio in Wheat Flours

¹Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66502. ²Departamento de Investigación y Posgrado en Alimentos, Grupo de Investigación en Química Agrícola y Manejo Postcosecha de Granos (GIQAMPO), Universidad de Sonora. Apdo. Postal 1658, Hermosillo, Sonora 83000 México. ³Corresponding author. Phone: +52-662-259-2208. Fax: +52-662-259-2209. E-mail: fcinco@guayacan.uson.mx

A comparison was made of methods for measuring the LMW/HMW glutenin subunit (GS) ratio for glutenin. A set of near-isogenic wheat lines with the number of HMW-GS varying from 0 to 5 was utilized to provide a wide range of LMW/HMW-GS. Glutenin preparations were obtained from ground whole meal after solubilization of monomeric proteins by dimethyl sulfoxide (DMSO) or 50% propanol or by fraction collection from a preparative SE-HPLC column. Analyses were made on the reduced glutenin from each of the three preparations by RP-HPLC, SE-HPLC, and SDS-PAGE. Both solvents, DMSO and 50% propanol, extracted appreciable amounts of polymeric protein, thus casting some doubts on the accuracy of the determinations. This problem was largely avoided when the polymeric fraction was collected from the eluate of a total glutenin extract run on a preparative SE-HPLC column. Less glutenin was removed by the two solvents for lines with a greater number of HMW-GS or with strength-associated HMW-GS 5+10 coded by the 1D chromosome. Collection of the polymeric protein in SE-HPLC, followed by separation of the glutenin subunits in RP-HPLC, was the best method for quantitating the LMW/HMW-GS ratio. SE-HPLC gave a clear separation of the two groups of subunits as well as HMW albumins. RP-HPLC has the potential advantage of being able to quantitate individual subunits.